The Islamic State group's beheading of a U.S. journalist and its threat to “destroy the American cross” suggests it has gained enough confidence seizing large areas of Iraq and Syria to take aim at American targets despite the risks.

On Tuesday night, Islamic State released a video showing a militant executing American freelance journalist James Foley. He was kidnapped in Syria nearly two years ago.

The black-clad executioner, who spoke English with a British accent, also produced another American journalist and said his fate depends on President Barack Obama's next move.

The beheading came as a surprise because the Sunni extremist organization had seemed focused on proclaiming a caliphate in the parts of Iraq and Syria it controls, marching on Baghdad and redrawing the Middle East map.

But in several telephone conversations with a Reuters reporter over the past few months, Islamic State fighters had indicated that their leader, Iraqi Abu Bakr al-Baghdadi, had several surprises in store for the West.

The fighters hinted that attacks on American interests or even on U.S. soil were possible through sleeper cells in Europe and the United States.

“The West are idiots and fools,” one fighter said. “They think we are waiting for them to give us visas to go and attack them or that we will attack with our beards or even Islamic outfits.

“They think they can distinguish us these days. They are fools and, more than that, they don't know we can play their game in intelligence. They infiltrated us with those who pretend to be Muslims and we have also penetrated them with those who look like them.”

Goading ‘hestitant brothers’

Another Islamic State militant said the group had practical reasons for taking on the United States.

"The stronger the war against the States gets, the better this will help hesitant brothers to join us," the fighter said. "America will send its rockets and we will send our bombs. Our land will not be attacked while their land is safe."

The Islamic State seems to be raising the stakes, aware that the gruesome death of an American and the image of another one at the mercy of an executioner who is taunting a U.S. president could invite retaliation.

It may be a way of improving its jihad credentials and attracting more followers and prestige in an Islamist militant world where taking on the “infidel” United States is a must.

Unlike al-Qaida, Islamic State did not at first seem bent on spectacular attacks on the West: It used fear to tighten its grip on the towns it seized in northern Iraq after facing little resistance from the U.S.-trained Iraqi army and Kurdish peshmerga fighters.

A video campaign?

But a series of videos it released recently – culminating with the one showing Foley's death – resembled footage that al-Qaida churned out while killing U.S. soldiers and slaughtering Shi'ites during the U.S. occupation.

The videos’ release followed the first U.S. airstrikes in Iraq since American forces withdrew in 2011. The airstrikes targeting Islamic State militants began August 8.

One recent video suggested the Islamic State was gearing up for an existential holy war between the caliphate and the crusader America, with the threat to destroy “the American Cross.”

In one scene, a purported American soldier weeps after losing a comrade and the Christian hymn “Amazing Grace” can be heard. In another, there is heavy breathing from the “Star Wars” movie character Darth Vader.

Iraq official decries ‘savage’ IS

Iraqi Foreign Minister Hoshiyar Zebari called on the international community to help his country battle the “savage” Islamic State.

But the United States and other Western powers may be diverting at least some attention away from the Sunni insurgents in northern Iraq to what they are capable of doing overseas.

The group can draw on hundreds, if not thousands, of foreigners with Western passports. That can keep them below the radar to carry out threats, like the British-sounding executioner in the Foley video.

Masrour Barzani, head of the Kurdish region's National Security Council, recently told Reuters he was concerned about Islamic State sleeper cells in the semi-autonomous Kurdish region in the north.

But he seemed equally anxious about a broader problem.

"Many of the members of [Islamic State] that have come from abroad have come from Europe, from the U.S., from the Middle East and North Africa – all over the world," Barzani said.

"These are people that are not going to die in battles in Iraq and Syria. Many of these people will go back to their countries of origin, becoming potential leaders or terrorist operatives, which could really become a bigger threat to their own countries."

Grave situation

Western countries are well aware of the issue – nine people suspected of planning to join Islamist militants in Syria were detained in Austria on Wednesday – but can they come up with tactics to tackle it?

French President Francois Hollande on Wednesday proposed an international conference to deal with security issues posed by the Islamic State group.

British Foreign Secretary Philip Hammond told the BBC, "We are absolutely aware that there are significant numbers of British nationals involved in terrible crimes, probably in the commission of atrocities, making Jihad with [Islamic State] and other extremist organizations."

Hammond said he didn’t "think this video changes anything. It just heightens awareness of a situation which is very grave and which we've been working on for several months."

Jamal Khashoggi, a long-time expert on al-Qaida who interviewed Osama bin Laden, said caution and security concerns may have kept Islamic State from carrying out attacks on Western targets so far.

But he predicted its militants, given the right conditions, would not hesitate.

"If they can blow up a suicide bomber in Times Square this afternoon, they'll do it," Khashoggi said. "What is keeping them from doing that is vigilance and security.

"But we have to admit that they are targeting all of us. If they can launch a terrorist attack in Riyadh, New York or London, they'll do that."